1. Field of the Disclosure
The following description relates to a carbon fiber composition and a fabrication method for carbon fiber. The carbon fiber composition includes nano-sized graphene, and the fabrication method for carbon fiber also uses the same composition. Through the method, a graphitization temperature for fabrication of high-performance carbon fiber (or graphite fiber) can be lowered.
2. Background of the Disclosure
Carbon fiber is a fiber-type carbon material having a diameter of 10 μm or less, which can be categorized according to a starting material (or composition) and a fabrication method into polyacrylonitrile (PAN)-based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, chemical vapor deposition (CVD)-based carbon fiber, etc.
The rayon-based carbon fiber was industrialized in 1963, and has been used as reinforcing fiber of a composite material in the various field, such as aerospace, etc. However, with the advent of PAN or pitch-based carbon fiber which can be manufactured at relatively-cheaper price, the production amount of the rayon-based carbon fiber has drastically decreased since 1978, and recently the production of the rayon-based carbon fiber has been actually stopped. Further, since the CVD-based carbon fiber has a problem of a low product yield, the PAN-based carbon fiber and the pitch-based carbon fiber are being mainly utilized in the carbon fiber-related industry.
Researches for enhancement of elastic modulus (elasticity) and strength of carbon fiber and for development of preparing method with lower costs, especially research on development of a new composition, is ongoing. As a method for enhancing physical property of carbon fiber, research on decrease of a diameter into sub micron (several hundred of nm) is also ongoing.
To prepare a high performance carbon fiber derived from PAN-based carbon fiber or pitch-based carbon fiber, a graphitization process should be performed at a very high temperature of about 2,500° C. or greater during the preparation process. Also, some kind of carbon fiber may be fabricated through a carbonization process at a temperature of about 800° C.˜1,500° C. only. However, in this case, the fabricated carbon fiber has lower performance than the high performance carbon fiber as mentioned above.
Since high-performance carbon fiber undergoes a graphitization process, it can be mentioned so-called “material of graphite structure”. Practically, it is reported that carbon fiber is composed of graphite ribbon (sheet-like, bent shaped, or loop shaped ones) [I. Mochida et al., Microstructure of mesophase pitch-based carbon fiber and its control, Carbon 34 (1996) 941-956 (FIG. 4); Chan Kim, Fabrications and Microstructural Characterizations of Multi-phase Carbon Nanofibers, J. of Future Fusion Technology 1 (2009) 19-25 (FIG. 9)]. The sheet-like graphite has a thickness of about 5-10 nm and a width of several μm, and the carbon fiber has a diameter of 10 μm or less.
Recently, graphene has attracted much attention. Graphene is a two-dimensional carbon material consisting of carbon atom with single layer having a thickness of about 0.4 nm. Since graphene is a basic unit of graphite (i.e., graphite is a stacked body with a plurality of graphene, it can be fabricated in the form of powder by decomposing graphite. Graphene powder can be defined as an accumulation of three-dimensionally random graphene layers.
Considering that a particle size of graphite is several μm, it may be understood that graphene powder obtained by decomposing the graphite have an average size of several nm˜several μm. However, an actual size of the graphene powder is a nano scale (1-100 nm).
Recently, the inventors of this disclosure have proposed a method for fabricating graphene powder by mechanical decomposing helical AA′ graphite (graphene helix stacked body) (Korean Registration Patent No. 10-1040967). Here, the graphene has a width of 5 nm or less than, a length of 20 nm or less than, and a thickness of carbon atoms to pure graphene of 0.4 nm.
Generally, carbon fiber and graphite fiber are considered to be the same meaning. However, carbon fiber and graphite fiber indicate fiber having undergone a heating process at 800° C.˜1,500° C. and fiber having undergone a graphitization process at 2,500° C. or more, respectively. Among carbon fibers used in the industry, high-performance carbon fiber of an excellent physical property (tensile modulus of about 350 GPa or more) means fiber having undergone a graphitization process at 2,500° C. or more. Through the conventional method of fabrication carbon fiber, it is impossible to lower a graphitization temperature for fabricating such high-performance carbon fiber, including PAN-based carbon fiber and pitch-based carbon fiber.
In the conventional art, there has been reports on technique of graphene composite nano (carbon) fiber. Here the graphene material is thin graphite having a thickness of about ˜10 nm, rather than graphene (referred to as ‘single-layered graphene’ or ‘multi-layered graphene’) [Sung-Yeon Jang et al., Graphene composite nanofiber and the preparation method thereof, Publication No. 10-2010-0099586].